Obviously if your original is lower quality (say, DVD) and your pirated backup is higher quality (say, Blu-ray) then I would concede that it's piracy of the difference (i.e., you're only entitled to backups at the quality you originally purchased) which can reasonably be considered piracy in full. For simplicity, let's suppose both originals are identical releases.
If a copyright holder would consider this to be piracy, logically they should also consider it piracy if you download your digital purchase multiple times without using the same CDN point of presence each time. I'm quite certain they'd consider that a non-issue, since it all shares a common ancestor (the master for that particular release) regardless of any meaningless duplication between the master and the licensed consumer.
I suspect it won't stand because the removal of the DRM provisions that potentially allow to retract access to the media is the point of, well, backing it up.
When you buy media DRM-free, you don't have to pirate anything, you can just peacefully make a copy.